Glacier responses to recent volcanic activity in Southern Chile

Glaciers in Southern Chile (39–43°S) are characterized by frontal retreats and area losses in response to the ongoing climatic changes at a timescale of decades. Superimposed on these longer-term trends, volcanic activity is thought to impact glaciers in variable ways. Debris–ash covered Glaciar Pichillancahue-Turbio only retreated slightly in recent decades in spite of been located on Volcán Villarrica which has experienced increased volcanic activity since 1977. In contrast, the negative long-term Volcán Michinmahuida glacier area trend reversed shortly before the beginning of the explosive eruption of nearby Volcán Chaitén in May 2008, when Glaciar Amarillo advanced and a lahar type of mudflow was observed. This advancing process is analysed in connection to the nearby eruption, producing albedo changes at Michinmahuida glaciers, as well as a possible enhanced basal melting from higher geothermal flux. Deconvolution of glacier responses due to these processes is difficult and probably not possible with available data. Much more work and data are required to determine the causes of present glacier behaviour. (letter)